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Mavis Batey, Allied Code Breaker in World War II, Dies at 92

After Britain declared war on Germany in September 1939, Mavis Lever, an 18-year-old British university student, volunteered to be an army nurse. Instead, because of her expertise in the German language, she was referred to the intelligence services.

“This is going to be an interesting job,” she recalled thinking, “Mata Hari seducing Prussian officers.”

But playing the role of temptress was not what the military had in mind for her. She was assigned to one of World War II’s most secret and important operations, an ambitious Allied effort to decipher secret codes used by the Axis powers — chiefly Nazi Germany’s mind-boggling one, aptly given the name Enigma. She was ordered to report to the unit’s headquarters, at Bletchley Park, a Victorian estate in southeastern England.

There, Miss Lever — one of the few women in the operation — was critical to at least two major successes in the war effort, including a British victory at sea in the Battle of Cape Matapan, off the coast of Greece, in March 1941, when an Italian convoy was ambushed and three heavy cruisers and two destroyers carrying 3,000 sailors were sunk.

When asked years later, after she had married and became Mavis Batey, she could hardly say why she, while still a teenager, was chosen for such a top-secret enterprise. But she did know that Dillwyn Knox, known as Dilly, a top code breaker at Bletchley Park, selected her for his team. In a largely masculine environment, Mr. Knox, an eccentric classicist by training, liked to hire women, especially pretty ones, and give them considerable responsibility.

Whatever the case, Mrs. Batey, who died on Nov. 12 at 92, more than justified her selection. The evening of the Cape Matapan success, John Godfrey, director of naval intelligence, called Mr. Knox at home and left a message: “Tell Dilly that we have won a great victory in the Mediterranean, and it is entirely due to him and his girls.”

The team at Bletchley Park — 12,000 people, including Americans, worked there at one time or another during the war — was composed, among others, of mathematicians, linguists, crossword mavens and an assortment of acknowledged eccentrics. Its existence was kept secret until the mid-1970s. Sir Francis Harry Hinsley, official historian of British intelligence during World War II, has said that the operation’s code-cracking work shortened the war by two or more years.

One of its chief challenges was decoding messages scrambled by what the Allies called Enigma machines. The device, used by the Germans and other Axis powers and resembling an oversize typewriter, used a series of electrical rotors to scramble messages in an astronomical number of ways; each letter could appear in more than 150 million million million permutations.

The messages, sent by radio using Morse code, were intercepted by spies and sent to Bletchley Park, where code breakers had access to their own Enigma machines, originally obtained by Poles and given to the British. A principal tool they used was a computerlike device, made by the genius mathematician Alan Turing, connecting a series of Enigma machines.

Photo

Mavis Batey with a German Enigma code-scrambling machine. She was assigned to one of the war’s most secret operations.Credit
Ian Jones

But Mr. Knox preferred to work through linguistic cues, which required thinking in sometimes counterintuitive ways. In his book “Enigma: The Battle for the Code” (2000), Hugh Sebag-Montefiore wrote that a question Mr. Knox asked potential recruits was which way the hands of a clock go around. Everyone, of course, said clockwise. A delighted Mr. Knox would reply, “Not if you’re inside the clock.”

One of Mrs. Batey’s hunches that proved accurate in deciphering code allowed the British to read a long, detailed message on Italian naval plans in the Mediterranean, paving the way for the Cape Matapan victory. The plans, she recalled, revealed “how many cruisers there were, and how many submarines were to be there, and where they were to be at such and such a time.”

“Absolutely incredible that they should spell it all out,” she said.

In December 1941, Mrs. Batey collaborated with her colleague Margaret Rock to decipher a small segment of a message by the German secret service. Not until years later did they know the effect: It helped British spies to learn that German generals believed that Allied forces would invade at Calais, France, not Normandy, on D-Day in June 1944.

Mavis Lilian Lever was born on May 5, 1921, in South London to a postal worker and a seamstress. Inspired by a vacation to Germany with her parents, she went on to study German Romanticism at University College, London.

But when the war broke out and she was assigned to intelligence duty, any thoughts of working as a spy were quickly dispelled. “I don’t think my legs or my German were good enough,” she told the British newspaper The Daily Telegraph in 2001, “because they sent me to the Government Code and Cipher School,” the official name for the Bletchley Park operation. It was also called Ultra and Station X.

At Bletchley Park, she fell in love with another code breaker, Keith Batey. They married in 1942. Mr. Batey, who died in 2010, went on to be the chief financial officer at Oxford.

And Mrs. Batey went on to write books about Mr. Knox and the experience of Ian Fleming, author of the James Bond novels, as a code breaker at Bletchley Park. A longtime president of Britain’s Garden History Society, she also wrote books on the landscapes of Jane Austen and the gardens of Oxford.

Her survivors include her daughters, Elizabeth and Deborah; her son, Christopher; and several grandchildren. The children knew nothing of their mother’s wartime exploits until files about the Bletchley Park operation were declassified.

In the 2001 movie “Enigma,” Kate Winslet at least partly molded her portrayal of the code breaker Hester Wallace on Mrs. Batey, with whom she had tea before shooting the film. Like Mrs. Batey, the Hester character falls in love with another code breaker and marries him.

Some Bletchley Park veterans criticized the film as inauthentic. Mrs. Batey’s criticism was that its women appeared “scruffy” compared with the originals. As she told another British newspaper, The Daily Record, in 2008, “We borrowed each other’s pearls, so we always looked nice.”

Correction: November 28, 2013

An obituary on Sunday about Mavis Batey, a code breaker for the Allies during World War II, misstated the given name of the character, partly based on Mrs. Batey, portrayed by Kate Winslet in the movie “Enigma.” Her name is Hester Wallace, not Heather.

A version of this article appears in print on November 24, 2013, on Page A32 of the New York edition with the headline: Mavis Batey, 92, Allied Code Breaker in World War II. Order Reprints|Today's Paper|Subscribe